1. Field of the Invention
The present invention relates to a device for resetting a computer system after lockup has occurred. More particularly, it relates to an electronic multi-line telephone control device which interrupts electrical power for a predetermined period of time in order to reboot an externally-operated computerized appliance.
2. Description of the Prior Art
Many different electronic systems have been developed for unattended operation at a remote location. One specific application is that of a modem used to allow access to a computer via a telephone line. From time to time, various factors cause a "lockup" of the computer, which renders it inoperative and inaccessible. Lockup occurs when the computer becomes disabled due to problems in reading or running various software programs. The software can deactivate the computer by becoming involved in an infinite loop or can become temporarily inoperative due to incorrect parameters entered by the user. Additionally, the computer may also incorrectly read program code into RAM from the computer hard disk or floppy disk.
Often, when lockup occurs, the only recourse is to reboot the computer and start afresh. Rebooting involves actually switching electrical power to the computer off and then on again. This ultimately clears or erases any software code stored in non-static RAM. The software code can then be read back into RAM from either the computer firmware in ROM, the system hard disk drive, or from floppy disks, and automatically restarted.
Special problems occur when the computer system is remotely operated by modem since no operator is present to reboot or reload software when the computer is in lockup. While in lockup, the computer is virtually useless and a trip must be made to the remote site in order to reboot the system. This results in much lost user time which can be inconvenient and expensive. Once the computer is rebooted, contact with users may then be re-established via an attached telephone modem.
Many different types of devices have been devised in order to remotely control computers and their peripherals such as modems, printers, etc. These devices operate primarily to turn on or off the computer peripheral by using a telephone line. The systems operate either through the use of telephone ring detection or specialized circuitry to detect DTMF tones dialed from the keypad of the telephone and typically use only one telephone line. If a computer is in lockup, the telephone line connecting the modem may also stay busy because the modem will not release or hang up the line. Under these conditions, a user cannot even use the telephone line to activate a remote device to turn off the computer.
For example, U.S. Pat. No. 3,876,836 issued to Langan relates to a remote control apparatus which utilizes a predetermined number of telephone rings to provide control effects at a remote site. A command or order to the apparatus in the form of telephone rings, from a user, is registered at a remote location by a counter. The counter activates a timer for setting up an inhibiting period. At the end of the inhibiting period, the counter is reset. A count of one (one ring) applied to the circuit activates an electrical outlet for turning on the remote device while two rings act to de-energize the electrical output for turning the device off.
This type of device has distinct disadvantages in that multiple rings equal to more than a preset count will not activate the device. The device uses only one telephone line, so if the line is busy, activation or deactivation is not possible. Further, this circuit will not accumulate rings over multiple or successive phone calls. Most importantly, the circuit does not "interrupt" the electrical power of the device. Interruption occurs when the device is turned off and then after an elapsed period automatically turned back on. This circuit merely turns the device off without automatically turning it back on after any predetermined set time. A completely separate procedure is required in order to reactivate the device.
U.S. Pat. No. 4,845,773 issued to Attallah also discloses a system for remotely switching electrically-operated devices using calling signals generated by a telephone. A detection circuit identifies a specific code of a telephone calling sound signal, and validates a predetermined number of such calling sound signals to determine if a switching function is to be performed. The user causes the telephone to generate a first series of repetitive calling signals, followed by a delay period and then further calls to generate a second series of repetitive calling signals, thereby causing a processing circuit to validate the calling signals.
U.S. Pat. Nos. 4,467,444 to Wilkerson, 4,996,706 to Cho, and 4,686,526 to Gritzo further disclose apparatus for controlling remotely-located devices through the use of ringing signals. Wilkerson operates by plugging the device into a wall outlet for switching AC power to the remote activation device. Cho relates to a method for controlling the power supply to a modem for transmitting or receiving data between a telephone and computer. The device operates so as to allow power to be supplied to the modem only when the user desires to transmit or receive data via the modem. When the modem is not in use, it is placed in a standby mode to decrease the power consumption and prevent generation of undesirable electromagnetic radiation. The patent to Gritzo relates merely to a computer reset system that acts as a stand-alone monitor and controller by clocking in each character sent by a terminal to a computer and comparing it with a given reference character. The reset circuit activates in response to detection of a proper condition or match.